Ecl = more neg than Em for a mammalian axon!!!
Ecl = more pos than Em for a squid axon (-60 mV)

What is the state of the resting Em?

Steady state - needs a constant supply of energy to be maintained.

What is the energy source for maintaining the resting Em?

ATP

How is the resting Em maintained?

Na/K ATPase

What does Na/K ATPase do?

Pumps 3 Na out per 2 K in

What is the effect of Na/K ATPase?

A net positive charge outside the cell and net negative inside.

Why is the Na/K pump needed?

Because Na and K leak across the membrane down their concentratio n gradients at a constant rate; if allowed to be unopposed, the gradients would dissipate and no potential difference would be available for establishing AP's and IPSPs/EPSPs!

How much energy is used by the RBC, resting squid axon, and resting frog muscle fiber for Na/K Atpase?

20%

For the retina how much energy is used for Na/K active transport?

Almost all of it

How is Na/K ATPase regulated?

By increasing intracellular Na or extracellular K

What will cause loss of Na/K pump action?

Ischemia or hypoxia

Why do ischemia/hypoxia stop Na/K ATPase?

Because they stop ATP formation and there's no more energy to pump the ions.

Why is the Na/K pump termed electrogenic?

Because it adds to the already negative cell interior by pumping out more positive charge than in.

So what 2 things contribute to the resting cell's negative interior?

-Ediffusion potential
-Eelectrogenic potential

What will cause an increase in the rate of the Na/K pump?

Any condition causing a significant increase in intracellular Na or extracellular K